KYOTO, Japan — Theresa May is finding it's hard to compete with the threat of a nuclear conflict.

The prime minister's visit to Japan was meant to be an opportunity to showcase the international trading potential of a post-Brexit "global Britain." But North Korean leader Kim Jong Un's decision to fire a missile over the north of Japan has stolen headlines and put an unwelcome focus on regional security.

May's attempt to lean on China over the issue then opened up a diplomatic spat with Beijing and other comments from the prime minister provided some distraction of their own.

Her vow to hang on to fight the next election ("I'm in this for the long term," she told reporters) looked set to dominate domestic headlines — and risked an angry response from a number of her backbenchers still smarting from the disastrous election campaign.

In all, not the post-Brexit trade message she hoped to send with the trip.

Over a dinner on Wednesday evening that included salted sea cucumber entrails, pike conger soup and lobster sashimi, May and Japanese Prime Minister Shinzō Abe discussed the North Korean missile test.

May told Abe that Britain “stood shoulder to shoulder with Japan in the face of North Korean aggression” and vowed to look deeper into additional sanctions should things not calm down, the prime minister's spokesperson said.

A screen in Tokyo shows the flight path of the North Korean missile | Toshifumi Kitamura/AFP via Getty Images

North Korea's actions will take center-stage again Thursday morning when May holds a national security briefing with Japanese and British navy officers on board a Japanese aircraft carrier.

But the prime minister's attempts to cajole China into doing more against Pyongyang proved more controversial. May's suggestion that Beijing had a key role to play “in terms of the pressure that they can bring on North Korea" drew an angry response from Beijing.

Foreign ministry spokeswoman Hua Chunying said those calling for China to do more "only pay attention to sanctions and pressure, and ignore peace talks.”

“When we promote peace talks, they ignore this," Hua said at a press briefing.

Brexit uneasiness

May will look to make a clean pivot Thursday by stepping up talks on trade with Abe and reassuring him about the impact of Brexit.

There is clearly work to do on that front. “Britain has always cut a special niche for Japan. There is an inherent preference among Japanese people and Japanese industrialists for doing business wherever possible in the United Kingdom,” Tomohiko Taniguchi, a special advisor to Abe, told the BBC's Today program on Wednesday. But, he added, “there certainly exists a sense of uneasiness [about Brexit].”

To prove she is serious, May brought with her the CEOs of 15 of the U.K.'s most influential businesses, including upmarket car brand Aston Martin, which announced a £500 million trade and investment deal Wednesday as part of its Japanese expansion.

"There are few places where the opportunities of doing [business] are greater than Japan, the third largest economy in the world," the prime minister will say Thursday.

May will also reiterate the U.K.'s desire to "quickly establish a new economic partnership between the U.K. and Japan based on the terms of the Japan-EU Economic Partnership Agreement" and "ensure the freest and most frictionless trade possible between the U.K. and the EU."

Amid the diplomatic noises, it remains to be seen whether the prime minister’s visit has provided the reassurance that the Japanese are seeking.

The U.K. wants to use the Japan-EU deal as the blueprint for its own trade agreement — something that may not be achievable given the U.K.'s smaller economic clout.

Even so, the U.K.'s trade minister, Liam Fox, will tell his Japanese counterpart Hiroshige Sekō at a meeting in Tokyo Thursday that trade ties between Britain and Japan will remain strong whatever happens after Brexit.

With £15 billion of value coming to the U.K. economy every year from the car sector, Britain is well aware of the disruption that could be caused should Honda, Toyota and Nissan decide it is no longer economical to manufacture their vehicles in Britain — for example if a U.K. manufacturing base no longer has access to the EU single market.

Amid the diplomatic noises, it remains to be seen whether the prime minister's visit has provided the reassurance that the Japanese are seeking.